Brownian Motion
by Mauve Alert
Summary: It happens completely by random. So many things do, when the Doctor is involved. Complete!
1. Chapter 1

_Title: _Brownian Motion

_Summary_: A man encounters the Doctor by chance. Companion of sorts to Denaturing.

_Disclaimer_: It doesn't belong to me. . . I'm just having a bit of fun.

_ A/N_: This takes place in the same universe as my story _Denaturing, _with the same OCs, but can be read on its own.

* * *

_I. _

It happens completely by chance.

Luke will learn eventually that many things do, when the Doctor is involved.

It is a matter of being in a certain place at a certain time. The cell at the government black site is a particularly unhealthy place to be, and it's just his luck that the Doctor and his blonde plus-one happen to have an invitation to the same party.

Years later, he will reflect that if he'd been arrested an hour earlier, he would've been dead before the Doctor got there; an hour later, and the secret police would have been the least of his worries. By then he'll have learned that the world always seems to be on the brink of destruction when the Doctor is around. This time is no exception, though he doesn't know it yet.

He will never be sure whether is better or worse that he was brought into custody at exactly the right moment to collide with the Doctor.

"Comfy," is the first word that he hears from the bespectacled, pinstriped stranger, when the two new prisoners are shoved roughly into his cell.

His teenaged companion giggles, as if she's been shown into a posh party rather than a drab gray cell. She doesn't appear to notice the restraints on her wrists. "I love the color scheme," she says. "Gray on gray. Very classy." She sidles over to him and awkwardly roots around in his pants pocket.

The pinstriped man _tsk_s. "Unoriginal," he disagrees. "They're always gray or white. For once I want to get thrown into fuchsia jail cell. Setting thirty-three, Anna, that's the ticket."

"For once I want to go somewhere _without_ getting thrown into a cell," says the girl - Anna? - pointedly, as she fiddles with the sonic device that she pulled from his pocket. A few clicks of a button later, their restraints are in the girl's back pocket.

Ever the opportunist, Luke decides that it's time to join this conversation. He's tempted to ask what she's saving the restraints for, but there's a more pressing matter at hand: they're unchained and he's not. "Go on ignoring me, thanks," he drawls. "I'll just be hanging out over here if you ever decide to, I don't know, let me down?"

"We didn't get thrown into a cell in Rome," the pinstriped man tells the girl. He slides a brief glance at Luke. "Hello!" he says cheerfully.

The teenager scowls. "Colosseum?" she reminds him pointedly. "Big, pointy swords? _Tigers_?"

A manic grin spreads over his face. "But no cell, that's my point. Oi, do you need a hand?" he adds, as if it's an afterthought.

"Oh, just let him down, Doctor, don't be a tease," says the blonde.

"What, me? Free a prisoner?" The man affects a scandalized expression, but finally whips out his sonic device and inspects Luke's bonds.

"Man rescues a couple of slave girls and he's insufferable for weeks," says the girl to Luke, as if expecting him to nod sympathetically and say, "I know what you mean."

Moments later, Luke collapses to the floor in a heap, massaging his wrists. "Thanks," he says, with only a touch of resentment. Well, two or three touches, anyway.

"Not at all." The stranger's voice is still pleasant, nonchalant. He doesn't seem to realize that they are in a place that most people have nightmares about. "Who are you, then?"

"Luke," he says, adding, "Out after curfew. You know how it is. You?"

"Anna," says the teen.

The man in pinstripes grins his crazy, cat-that-stole-the-cream grin. "I'm the Doctor."

"Just the Doctor," Anna chimes in.

Anna and the Doctor laugh giddily.

The future does not bode well.

* * *

Like it? Hate it? Please tell me what you think! 


	2. Chapter 2

A/N - Luke's story, continued. Big thanks to my reviewers!

* * *

_II._

Luke holds his mother's hand as the line goes flat, the skin goes cold. Feeling bits of his heart chip off and fall away, he brushes a kiss on her wrinkled forehead.

"Bye, Ma," he says, and lets go.

Humans have gone to space, made contact, evolved and mingled until most people aren't even _Homo sapiens_ anymore. There are spaceships and colonies on remote little moons and laser guns.

Nothing's changed, not really. There's just new ways to make people suffer, new ways to make people die.

The hospital is state-run, shiny and white and reeking of disinfectant. Luke has been fighting the power, so to speak, ever since the Doctor and Anna freed him from the black site prison cell, and it rankles him that it was this government facility that made his mother's last months as comfortable as they could be.

Things are the same as they've ever been, Luke thinks. Doctors still swear the Hippocratic oath.

He closes the door on his dead mother's room and freezes.

"I hate hospitals," declares a man's voice.

A girl laughs, a hauntingly familiar laugh. _It can't be_, Luke thinks desperately. "_You_ hate hospitals." She speaks with an accent he's only ever heard once before.

The unfamiliar man's voice is sullen. "You battle a bunch of Machiavellian cat nuns and see how _you_ like it."

"What do cat nuns have to do with hospitals?" A pause. "Cat nuns?"

Luke steels himself and looks at the source of the voices.

It's Anna. She's older now, maybe in her twenties, carrying a bundle that looks suspiciously like a baby. The man beside her is ginger-haired and wears thick square spectacles. Luke is immediately suspicious.

He tries to keep his head down as the pair pass. Where Anna is, the Doctor is sure to be close by, and the last thing Luke wants is to get tangled up in the Doctor's web.

A few years ago, he resisted the lure of the Doctor and his young companion, walked away from the big blue box. Now, his last link to this world is dead in the room he just left, and he knows he wouldn't escape a second time.

"Ohmigod!"

Anna has spotted him. She yanks on the man's arm with her free hand and babbles out. "It's him, that. . . guy! From the cell, remember, Doctor?"

"Which cell?" asks the man called 'Doctor' sardonically. Luke shuts his eyes and sternly tells himself that it isn't the same Doctor, it can't be. If the Doctor really can change his face, like the bedtime stories say, then all manner of other things that the bedtime stories say about him could be true, too.

"Dystopian future? Out after curfew?" Anna prods him.

"That narrows it down." Luke gets the impression that the man would roll his eyes if he didn't consider the expression beneath him.

"- It was early on, long time ago. What was your name?" This last question appears to be aimed towards Luke, but she steamrolls on without giving him the opportunity to answer. "L-something. Laurence? No, it was shorter, gimme a second..."

"Luke," says the man called Doctor, and Luke knows.

"It's true," he says.

The Doctor arches a brow, with none of Anna's amusement at meeting him again. "What's true?"

"What the bedtime stories say," Luke says, remembering his mother's gentle, laughing voice, spinning webs of adventure to wrap him up like blankets and drag him into dreams. "About the traveler who can change his face."

"You're a fairie tale!" Anna pouts. "How come I don't get to be a fairie tale?"

"Because you're not the Time Lord who's been saving the universe for the past millenia or so," says the Doctor shortly.

"Not fair."

The no-doubt cunning retort that the Doctor opens his mouth to utter is cut off when the floor suddenly pitches several feet to the left and the corridor goes dark. The bundle in Anna's arms lets out a high wail.

"Will you shut her up?" the Doctor snaps, already in Dealing With Trouble mode. The memories of another adventure, not too long ago, come rushing to the forefront of Luke's mind.

He knows how this is going to end.

_Bye, Ma_, he thinks. _Bye, home_.

It's unlikely he'll ever be back.

­

* * *

Like? Hate? Please tell me what you think!  



	3. Chapter 3

_A/N - _Sorry for the delay. I've been having computer troubles lately.

Hope you like the update.

* * *

_III._

"Goodbye," Luke says, the word bitter and strange on his tongue. He uses the bags he holds as an excuse not to shake the Doctor's hand.

The Doctor nods, face unreadable. "You won't stay until I find the baby a home, then?"

He won't stay. Anna is dead, and he can't stay. It's wrong, to be with the Doctor when Anna isn't. The place is hers, not his, and he refuses to take it. He won't, can't, replace her.

Aloud, Luke says nothing, but that doesn't matter. The Doctor can read minds.

"I'll let you know when things are settled," says the Doctor after a pause. "You'll keep an eye on her?"

The baby, Anna's beloved baby. It's a reason to go. An excuse. Someone needs to look after her and the Doctor obviously won't. "Yes. Anna would want it." Accusation creeps into his voice; he does nothing to stop it. "You'll just move on after that, won't you?" The edge is there. Luke is an unwilling satellite trapped in the Doctor's orbit, and the resentment is tangible.

The Doctor keeps his tone neutral, emotionless, and Luke hates him with more passion than he's ever felt about anything in his life. "That's right."

The anger and the hurt boils over. "After all those years. You were her life. There was nothing she wouldn't do for you, wouldn't give for you, and you're just going to drop her baby with a couple strangers and find some other girl to give her life for you." He sneers, the words pouring out like so much bile. "That's what all the fairie tales and bedtime stories say, isn't it? There's always the Doctor, and always a pretty girl following him into certain death. You're partial to blondes, aren't you?"

Something flashes in the Doctor's eyes. Luke is absurdly pleased by that hint of unbridled feeling. "Humans. You're always going on about free will and then finding someone else to blame."

"And yet you keep on dragging us in, don't you, _Doctor_?" He bites out the title like a curse. Here he is, at the TARDIS door, so close to escape, on the verge of running back into the ship's labyrinthine corridors and never coming back. His head feels as if it is filled with helium. Even if he does walk out into 21st century Boston and never sees the Doctor or his blasted blessed TARDIS again, he knows that he'll never truly be free. The Doctor is a black hole, trapping those around him by sheer force of gravity and pulling, pulling, pulling, until they're obliterated into nothingness. "Just keep pulling and pulling and pulling and you never let go."

"Leave. I'm not stopping you," says the Doctor, with his own brand of quiet, simmering anger.

Realizing he's been dismissed, Luke nods and pulls open the door. He has no idea where he's going, what he'll do in a strange city in a strange century. He just has to leave. "Let me know when you find the baby a place," he says.

"I'll find you," the Doctor replies.

Luke has no doubt that he will.

* * *

Like? Hate? Let me know! 


	4. Chapter 4

The Doctor and Luke meet again. Enjoy.

* * *

_IV._

The TARDIS is sitting on the sidewalk.

It looks so innocuous, basking in the bright spring sunlight. Just a blue police box on a beautiful day, it seems to say, nothing odd about this, nope, just move along and everything will be peachy-keen.

It's mocking him.

Luke knows this story. It's all sunshine and smiles, and then the Doctor shows up, a grin on his face and a girl on his arm, spouting some inane historical trivia or a bad joke about bananas. He wanders around for awhile, flirts with the locals, and. . .

BAM.

Trouble.

Yeah, Luke knows this game and he's not having any of it, not anymore. He's done with the Doctor, has been for a long time now. He severed those ties when he walked out the TARDIS door for the last time.

There's only Sophie, Anna's baby, that links them now, that one fragile connection to his past, to the Doctor, to Anna. In that regard, at least, the Doctor was true to his word. He found the baby a family, named her, and informed Luke of her whereabouts. And then he was gone, and Luke hasn't seen or heard from him since.

Until now.

_No_, he tells himself, because denial is really all he has left. He turns his back to the TARDIS and focuses on the task at hand.

Before him is a crowd of eighth-graders, loud eighth-graders jittering with caffeine buzzes and hormones and those two magic words, _field trip_. If someone had told him, years ago, that he'd end up in twenty-first century Boston teaching middle school science. . .

It doesn't do to dwell on the past, so Luke shoves that thought away. He focuses on dividing the sea of adolescents into groups, assigning them to already exhausted-looking chaperones. He picks out Sophie's face in the crowd, so like Anna's, and because the TARDIS is sitting on the sidewalk behind him, he puts her and her friend in his group.

She basks in the sunlight, face aglow, a thirteen-year-old girl in love with the world. She has a bit of a crush on him, he's noticed. It's fairly normal in girls her age. Hormones. Normally it wouldn't bother him, but this situation strikes him as awkward, simply because it's _Sophie_. He knows things about her that she's not even aware of, the circumstances of her birth and what happened to her biological parents, while she has no idea that he's anything but her science teacher.

But she's a good kid, sweet, and he's glad that she knows nothing about her past - that she knows nothing about the Doctor. She's innocent, unmarked.

Sophie smiles at him, Anna's smile. He grins back. Then, her eyes land on something behind him and the smile drops away. Without looking he knows what it must be.

The TARDIS.

She knows it. She's seen it before.

A horrible sinking feeling in his gut tells him that Sophie is not quite so innocent when it comes to the Doctor, and his world goes a little darker.

They're in the exhibit hall when Luke spots him, examining a display a few yards away. After a moment, the Doctor turns and meets his stare.

They begin walking towards each other at the same time and meet somewhere in the middle.

"You," the Doctor says. He seems jumpy, twitchy. "Why are you here?"

Luke is skeptical. He knows the Doctor's game. "I live here!"

The Doctor arches his eyebrows and bounces on his heels. "What, in the museum?" This version of the Doctor is much more obtuse than his previous incarnation. Luke still hasn't figured out how much of it is an act.

"No, in Boston," he snaps, already exasperated.

"I knew_ that_." Behind the square glasses, the Doctor's blue eyes light up. "You're investigating, is that it? Always were suspicious, you."

"No." It is a hard, flat syllable, that _no_. He likes it. Twenty-first century English has many interesting sounds, but this might just be his favorite. "No, I'm chaperoning a field trip. I'm a teacher."

"Oh," the Doctor says, scanning the room over Luke's shoulder. "Oh. Well, leave you to it, then. Might want to take the class trip somewhere else, incidentally. Got a spot of trouble here."

Trouble.

"You're not just spying on Sophie?" he blurts, horrified. He's been hoping that this is the case, the Doctor is just popping into town to see Sophie before swanning off on his merry way. But no, there has to be Trouble. It follows the Doctor wherever he goes like a black storm cloud on a bad day.

"Sophie," the Doctor repeats, genuinely confused. "What's she got to do with it?"

"She's here. On the trip. She's a student of mine." He jerks his head towards his group of students, where Sophie and her friend Jessa are giggling over something.

The Doctor skewers Sophie with a steely blue stare. For a moment, Luke thinks he sees her flinch, though her back is turned. "Get her out. Get them all out, now."

"Why? What's going on?" _What have you gotten mixed up in now?_

The Doctor makes a wide gesture, eyes sparkling with manic exictement. Luke knows this look. It's a harbinger of explosions to come. "See this exhibit? Alien artifacts?"

Luke nods; he chose this exhibit because he was curious about how accurate it would be. "Some of them are even real," he says dryly.

The Doctor doesn't laugh. "That's right. And there are some seriously angry aliens here that want their property back."

Luke lets out a curse word that hasn't even been invented yet. "I'll get the kids out of here."

The Doctor nods. "I'm going down to security, get an evacuation started."

To use Anna's words, they Spring Into Action.

He alerts the chaperones and gets the kids back on the buses. He checks on Sophie; she's pouting about the field trip being cut short. He smiles at her, thinking of a little baby in another brave Boston girl's arms, and then he goes back inside.

The Doctor isn't surprised to see him run up the empty hall. He simply slaps the sonic screwdriver into Luke's hand and says, "Setting 42 b, Luke."

Twice Luke has walked away from the Doctor. He's not so strong or lucky to escape again.

* * *

Love it? Hate it? Tell me what you think!  



	5. Chapter 5

_A/N_ - We've reached the end of another story! Not sure where I'm going next, but there is another story in the works set in this universe, so keep an eye out.

Thanks to everyone who read and reviewed, particularly CentaurGirl42, Kates Master, and Templremus1990.

As always, concrit is welcome!

* * *

_V._

Boston, Massachusetts. April 9th, 2032.

The date echoes in his mind, somehow familiar. Important. He has the vaguest memory of it. . . a history class in a different time, a different world, so very far away. He memorized it, once upon a time - for a test, he recalls, back when he'd been on the other side of the red pen.

What happened on that day? _Today_, he corrects himself. He's here, now, on the day that the bomb drops.

The bomb.

The memory comes back in a rush. Boston bombed. The First Nuclear War, and no one remembers why.

Here. Today. _Now_.

The TARDIS has brought them right to volcano day, and the reason why is very clear. Sophie, grown up since he saw her last, is struggling as the Doctor attempts to drag her towards the ship. She has the right to resist- after all, the Doctor has just run up to her on the street, grabbed her hand, and ordered without preamble, "Run!"

For once, Luke agrees with his methods. They need to leave, and soon, or the bomb is going to blast them all into oblivion.

"I knew your mother," the Doctor is saying to Sophie, pleading. "I know you."

They both tried to protect her, in their ways - the Doctor by giving her up, Luke by staying with her - but the Doctor left her in the wrong time and place, and Luke put her on the bus and ran onto the TARDIS once more, not strong enough to walk away again, even for her.

Neither of them could stand to lose her; they made promises to Anna, to Sophie, two Boston girls with ridiculous accents and bright smiles. This is Sophie, Anna's baby, the child they have loved so much and failed so greatly, and they will not let her die here. In this, at least, they are the same.

Sophie searches their faces. When her eyes meet his, he nods in recognition, greeting, and, he hopes, recognition. He can't speak - he doesn't know what to say. _Run_, but with them or from them, he isn't sure. Nothing's been certain since the Doctor and Anna swanned into his cell all those years ago.

_Well_, he amends. One thing is very certain: they have to get out of this place before a fifty-megaton nuclear bomb turns them into dust. "Doctor," he says urgently. The sky is blue, cloudless. Sunlight and smiles, but not for long.

Sophie stares at him, long and hard; she's grown up since he saw her last, but somewhere in her eyes is a remnant of the trust a student had in her teacher, that adolescent crush she'd nursed. _Please_, he begs her silently.

The Doctor stretches out his hand. The moment, anxious and confused and tense, seems to stretch into infinity.

Sophie takes the Doctor's hand. The spell breaks.

They run for their lives, and make it back to the TARDIS just in time.

_It's blind luck_, Luke thinks, holding Sophie tight as the world outside the TARDIS explodes. There's no equation for the points where their lives intersect. It's just chance that the Doctor and Luke happened to be in those same places- the jail, the hospital, the science museum - in those _exact_ times. It's just chance that they've landed in precisely the right place and time to find Sophie.

It's all completely random.

So many things are, Luke knows, when the Doctor is involved.

-FIN-

Like? Hate? Let me know!


End file.
